This invention relates generally to a safety device for on/off switch of an electric tool, particularly to a safety device for an on/off switch that can actuate an electric tool only when a user operates a specified start component with both hands simultaneously so as to avoid any unexpected action of the electric tool, which might be caused by an accidental touch with a single hand, and thereby ensure a user""s safety in using that electric tool.
Without exception, an electric tool is provided with an on/off switch for control operation of its motor. For example, a horticultural electric tool with trimming knife is usually provided with a trigger for a user to pull or release to drive or stop the tool.
In many cases, a single trigger is provided to a conventional electric tool for power on/off control, hence, it is a worry of latent danger in the case of a stand-by horticultural electric tool, which could be casually triggered by a user to drive the knife attached thereon that might hurt the user himself unexpectedly.
The primary objective of this invention is to provide a safety device for on/off switch of an electric tool, comprising a trigger and an interrelated knob. A user has to operate the trigger and the knob with his two hands simultaneously to switch on the power successfully, otherwise he would fail to do so should he use either hand only. Under this operation condition, any unexpected harm done upon a user by touching the trigger or the knob carelessly with a single hand is avoidable.
In order to realize abovesaid objective, the safety device for on/off switch of an electric tool comprises a casing having a switch and a link assembly. The link assembly is composed of a knob, a first link lever, a second link lever, a trigger, and a dog, in which the trigger, the second link lever, and the knob are pivotally jointed to the casing; the first link lever is pivotally jointed with the trigger; the second link lever is pivotally jointed with the first link lever; the knob is pivotally jointed with the second link lever; a dog is pivotally with the first link lever, and a protruding portion of the dog is positioned corresponding that of the switch. In the event when the trigger or the knob is depressed only by a single hand, the dog is pulled to have its protruding portion lifted to a position near the switch, or when both the trigger and the knob are depressed simultaneously, the dog is pulled to travel a longer-distance stroke to have its protruding portion pressed against the switch for actuating the power, such that a careless or casual touch onto the trigger or the knob by a single hand cannot switch on an electric tool to thereby avoid doing any unexpected harm to a user.
For more detailed information regarding advantages or features of this invention, at least an example of preferred embodiment will be fully described below with reference to the annexed drawings.